There is a need for amphibious marine vehicles to discharge troops and cargo at beachheads that are based on newer higher speed hull designs than currently available. As an example of currently available landing craft, consider that the Navy's LCU (Landing Craft Utility) has a top speed of about 12 knots and is beachable but not amphibious.
An alternative is the LCAC (Landing Craft Air Cushion) that is not only beachable but also amphibious. The LCAC is supported by a blower pressurized air cushion. The LCAC has a full 360 degree peripheral flexible skirt that attaches to the underside of its hull and restrains the air cushion between the hull and a water or land surface. The LCAC and its like are many times referred to as hovercraft. The LCAC has a number of inherent disadvantages, to wit: 1) It does not handle rough seas well, 2) It has an inherent rough “cobblestone” ride due to pressure perturbations in its air cushion where the pressure perturbations are mainly attributed to its full 360 degree flexible seals, 3) It is very weight sensitive, 4) It can only access beachheads that have gently sloped beaches, 4) Its full 360 degree flexible seals are expensive initially and to maintain, 6) Largely due to its need for power from three 4,500 HP gas turbines that supply propulsion and blower power, it is expensive initially with a current price of over $20 million, and 7) It is very noisy due to its necessary air propellers. In spite of these shortcomings the LCAC has been procured in reasonably large numbers due to its very valuable amphibious and 45 knot speed capabilities. The amphibious capability allows driving up onto a beach and discharging troops and cargo on dry land above the surf line.
The current Navy/Marine Sea Basing program has pointed out the need for beachable reasonably high speed marine transports that are referred to as HSCs (High Speed Connectors). The concept behind Sea Basing is to have large supply ships positioned about 200 miles offshore with troops, supplies, vehicles, etc. transported to beachheads by the HSCs. Some of Applicant's other patent application(s) address this need in the form of large beachable air cushioned marine vehicles. These inventive concepts of Applicant are mostly related to the SeaCoaster® SECAT (Surface Effect CATamaran) high speed marine vehicle.
The instant invention advanced marine vehicle proposed herein offers reasonably high speeds based on generally existing and proven hull designs that are rendered amphibious by used of the instant invention technology. This is accomplished by use of retractable land or other hard surface drives that are stowed upward between, forward of, or aft of water contacting hulls when the vehicle is operating on a water surface. This retraction upward of the land drives reduces the water contact of the drives during marine operation of the vehicle thereby reducing water drag. Some of the multi-hull types that this inventive technology may be applied to, but not limited to, include catamarans (two water contacting hulls), trimarans (three water contacting hulls), quadramarans (four water contacting hulls), pentamarans (five water contacting hulls), and the like. For best efficiencies, a trimaran and a pentamaran would normally have a single long and slender main hull with the extra hulls in outrigger hull arrangements to add stability and allow a wider deck. It is also to be noted that a quadramaran may consist either of four independent parallel hulls or sets of fore and aft hulls in an overall catamaran arrangement. It is to be noted also that the instant invention technology can be added to applicant's SeaCoaster® or other of his multi-hulled air cushioned marine vehicle inventions as well.